Comparison of effects of marihuana cigarettes of three different potencies

Abstract

Marihuana cigarettes containing 1.32%, 1.97%, and 2.54% delta 9-tetrahydrocannabinol (THC) were smoked by six experienced marihuana users at weekly intervals in a double-blind cross-over design under laboratory conditions. Puff duration, number of puffs taken, duration of inhalation holding, interval between puffs, and duration of smoking were recorded for each cigarette smoked. The portion of each cigarette remaining after smoking was weighed and analyzed to determine THC content. Subjective ratings of the "high" achieved and the heart rate acceleration induced by smoking the marihuana were measured. The plasma concentrations of THC and of its principle metabolite, 11-nor-delta 9-THC-9-carboxylic acid (9-carboxy THC), were determined by radioimmunoassay of blood samples drawn at frequent intervals for 6 hr. The results indicate that, irrespective of the potency of the marihuana, the pattern of smoking was much the same. The magnitude of the subjective high, heart rate acceleration, THC, and 9-carboxy THC plasma concentrations were proportional to potency. This dose response was particularly clear between the 1.32% and the 2.54% cigarettes. Peak plasma concentrations of THC consistently occurred 7 to 8 min after initiation of smoking and declined thereafter despite continued smoking for another 6 to 10 min. Peak subjective high and peak heart rate acceleration occurred several minutes after the end of smoking and at a considerable interval after maximal THC plasma concentrations were reached.

Self-administration of cannabinoids by experimental animals and human marijuana smokers

“…Studies using marijuana cigarettes with maximal THC contents ranging from 1.24 to 2.54% did not observe a significant titration of THC intake (e.g., Cappell et al, 1973;Perez-Reyes et al, 1982;Wu et al, 1988;Chait, 1989;Kelly et al, 1994a), while studies which observed a significant titration of THC intake used cigarettes with maximal THC contents ranging from 3.9 to 4.0% (Herning et al, 1986;Nemeth-Coslett et al, 1986). It appears that the ability of subjects to discriminate between different dose levels of THC might affect their marijuana smoking behavior.…”

“…During the following quarter century, scientists attempted, mostly with little success, to further demonstrate a THC dose-regulation phenomenon with smoked marijuana (Ashton et al, 1981;Perez-Reyes et al, 1982;Wu et al, 1988;Chait, 1989;Zacny and de Wit, 1991;Kelly et al, 1994a, but see also: Azorlosa et al, 1992;Harder and Rietbrock, 1997;Block et al, 1998). However, Herning and colleagues (1986) observed that experienced marijuana smokers took significantly more puffs with longer intervals between puffs while smoking high potency (3.9% THC) compared to low potency (1.2% THC) marijuana cigarettes and they also inhaled substantially larger (46%) volumes of air.…”

“…Using a 100-point scale, the subjects in the study by Heishman et al (1989), who adjusted their smoking of cigarettes that varied in THC content, also did not report differences in "drug high" or being "stoned" between 1.2 and 2.7% THC cigarettes, but they were not asked to evaluate potency. There have been dose-dependent increases in reports of subjective-effects ratings in several studies investigating regulation of smoking patterns with different THC-content marijuana cigarettes, regardless of the range of THC contents in the marijuana cigarettes used (low range of THC contents: Perez-Reyes et al, 1982;Chait, 1989; high range of THC contents: Herning et al, 1986;Zacny and de Wit, 1991). However, there have been studies using marijuana cigarettes with higher ranges of THC content that did not observe this tendency.…”

Marijuana Smoking: Factors That Influence the Bioavailability of Tetrahydrocannabinol

“…The results of clinical studies of marijuana cigarette smoking (Perez-Reyes et al 1982) indicate that, on the average, smokers puff more often (2.6 puffs per minute) than the puff frequency used in the Davis cigarettesmoking study (2 puffs per minute) (Davis et al 1983). Therefore, it is reasonable to assume that when subjects smoke marijuana cigarettes, the amount of THC lost in sidestream smoke is not as large as that found in the cigarette-smoking-machine experiments.…”

“…We have conducted studies in which the number of puffs, the puff duration, the interval between puffs, and the duration of marijuana cigarette smoking of similar or different (Perez-Reyes et al 1982) potencies were measured. However, in these studies, the critically important puff volume parameter was not measured.…”